Samuwar Tarko Mai Juyawa da Hasken Rana ke Haifarwa a cikin Perovskites na Gauran Halide don Photovoltaics

Table of Contents

1. Gabatarwa & Bayyani

Perovskites na gaurayawan kwayoyin halitta da inorganic, musamman nau'ikan gaurayawan halide kamar (CH₃NH₃)Pb(Br_xI_1-x)₃ (MAPb(Br,I)₃), sun zama kayan aiki masu ban sha'awa don ingantaccen amfani da hasken rana mai tsada. Wata muhimmiyar fa'ida ita ce ikon daidaita bandgap na gani ($E_g$) ci gaba daga kusan 1.6 eV (mai yawan iodide) zuwa 2.3 eV (mai yawan bromide) ta hanyar bambanta rabon halide (x). Wannan daidaitawar ta sa su dace da aikace-aikacen tantanin hasken rana guda ɗaya da na haɗin gwiwa. Duk da haka, ƙalubale mai ci gaba shine gazawar tantanin hasken rana na gaurayawan halide perovskite don cimma manyan ƙarfin lantarki na buɗe kewayawa ($V_{OC}$) da ake tsammani daga manyan bandgaps lokacin da abun ciki na bromide ya yi yawa (x > 0.25). Wannan aikin yana binciken asalin wannan rashi na ƙarfin lantarki, yana gano wani abu mai juyawa, wanda haske ke haifarwa wanda ke iyakance aiki sosai.

2. Babban Bincike & Sakamakon Gwaji

Binciken ya bayyana wani sauyi mai ƙarfi da juyawa a cikin fina-finai na MAPb(Br,I)₃ a ƙarƙashin haskakawa, tare da sakamako kai tsaye ga kaddarorinsu na lantarki da gani.

2.1 Canje-canjen Kaddarorin Gani a Ƙarƙashin Haskakawa

A ƙarƙashin haskakawa mai daidaito da rana ɗaya (100 mW/cm²), bakan photoluminescence (PL) na perovskites na gaurayawan halide yana fuskantar babban canji a cikin ƙasa da minti ɗaya. Sabon kololuwar PL mai juyawa zuwa ja ya bayyana a kusan 1.68 eV, ba tare da la'akari da bandgap na farko na gawa (don x > ~0.2) ba. A lokaci guda, sha na ƙasa-bandgap yana ƙaruwa a kusa da 1.7 eV. Waɗannan abubuwan lura sune alamun alamar samuwar sabbin jihohin tarko na lantarki a cikin bandgap na kayan. Waɗannan jihohin suna aiki azaman cibiyoyin haɗuwa marasa haske, waɗanda galibi suna rage yawan amfanin photoluminescence quantum kuma, mahimmanci ga tantanin hasken rana, suna rage $V_{OC}$.

2.2 Shaidar Tsari daga X-ray Diffraction

Aunin X-ray Diffraction (XRD) ya ba da haske na tsari. Bayan haskakawa, an lura da raguwar kololuwar XRD guda ɗaya mai siffa ta lokaci ɗaya na gaurayawan halide. Wannan raguwar kololuwar shaidar kai tsaye ce ta rabuwar lokaci, yana nuna cewa kayan sun rabu zuwa yankuna na crystalline daban-daban tare da ma'auni daban-daban na lattice.

2.3 Juyawar Abubuwan da ke Faruwa

Wani muhimmin bincike da ban mamaki shine cikakkiyar juyawar wannan tsari. Lokacin da aka sanya samfurin da aka haskaka a cikin duhu na mintuna da yawa, kololuwar PL mai juyawa zuwa ja ta ɓace, sha na ƙasa-bandgap ya ragu, kuma kololuwar XRD ta koma siffar layinsu na asali, lokaci ɗaya. Wannan juyawar ta bambanta shi da hanyoyin lalacewar hoto na dindindin.

3. Tsarin da aka Tsara: Rabuwar Halide

Marubutan suna hasashen cewa abubuwan da aka lura suna haifar da rabuwar halide da hoto ke haifarwa. A ƙarƙashin hoto, ana samar da nau'ikan lantarki da rami, suna haifar da ƙarfin tuƙi na gida don ƙaura ion. Ana imani cewa ions iodide (I⁻), waɗanda suka fi motsi da polarizable fiye da ions bromide (Br⁻), suna ƙaura da taruwa tare, suna samar da yankuna masu yawan iodide. Akasin haka, matrix ɗin da ke kewaye ya zama mai wadatar bromide.

Wannan yana haifar da tsari iri-iri: yankunan masu yawan iodide suna da bandgap mai kunkuntar (~1.68 eV) fiye da matrix ɗin da ke kewaye mai wadatar bromide. Waɗannan yankuna masu ƙarancin bandgap suna aiki azaman ingantattun "rikitattun" ko tarko don masu ɗaukar caji na hoto. Sun zama manyan cibiyoyin haɗuwa, suna ɗaure makamashin fitar da PL kuma, ta hanyar ƙari, rabuwar matakin Fermi wanda ke ƙayyade $V_{OC}$ a cikin tantanin hasken rana, zuwa ƙananan bandgap na lokacin mai yawan iodide.

4. Abubuwan da ke Tattare da Ayyukan Photovoltaic

Wannan tsari yana bayyana kai tsaye rashin aikin $V_{OC}$ na tantanin hasken rana na gaurayawan halide perovskite, musamman waɗanda ke da babban abun ciki na bromide da aka yi niyya don manyan bandgaps. Duk da fina-finai na farko, masu daidaitawa tare da babban bandgap (misali, 1.9 eV), a ƙarƙashin yanayin aiki (hasken rana), kayan suna samar da yankuna tarko masu ƙarancin bandgap (1.68 eV) ta zahiri. $V_{OC}$ na na'urar ya zama iyaka da waɗannan yankuna maimakon bandgap ɗin da aka yi niyya. Wannan yana wakiltar hanyar asarar inganci na asali da kuma babban ƙalubale ga kwanciyar hankali na perovskites na gaurayawan halide a cikin na'urorin lantarki da gani.

5. Cikakkun Bayanai & Bincike

5.1 Bayanin Lissafi na Daidaita Bandgap

Bandgap ($E_g$) na gaurayawan halide perovskite MAPb(Br_xI_1-x)₃ baya bin ka'idar Vegard mai sauƙi amma ana iya bayyana shi ta hanyar gwaji. Don kiyasin farko, ana iya ƙirƙira daidaita bandgap tare da abun da ke ciki $x$ kamar haka: $$E_g(x) \approx E_g(\text{MAPbI}_3) + [E_g(\text{MAPbBr}_3) - E_g(\text{MAPbI}_3)] \cdot x - b \cdot x(1-x)$$ Inda $b$ shine sigar baka da ke lissafin aikin da bai dace ba. Samuwar yankuna masu yawan iodide a ƙarƙashin haske yana rage $x$ na gida zuwa kusan 0, yana mayar da $E_g$ zuwa ~1.6 eV.

5.2 Tsarin Gwaji & Tsarin Binciken Bayanai

Misalin Tsarin Bincike (Ba Code ba): Don gano rabuwar da hoto ke haifarwa a cikin saitin dakin gwaje-gwaje, ana iya kafa ka'ida ta yau da kullun:

1. Bayanan Tushe: Auna bakan PL na farko, bakan sha, da tsarin XRD na fim ɗin da ba a taɓa shi ba a cikin duhu.
2. Gwajin Danniya na Haskakawa: Haskaka samfurin tare da na'urar kwaikwayon rana da aka daidaita (Rana 1, bakan AM1.5G) yayin lura da bakan PL a ainihin lokacin ta amfani da spectrometer mai haɗin fiber.
3. Binciken Kinetic: Zana ƙarfin kololuwar PL mai bayyana ~1.68 eV akan lokacin haskakawa. Dace da bayanai zuwa tsarin kinetic na farko: $I(t) = I_{max}(1 - e^{-t/\tau})$, inda $\tau$ shine lokacin da aka saba da shi don rabuwa.
4. Duba Juyawa: Dakatar da haskakawa kuma ku lura da raguwar kololuwar 1.68 eV a cikin duhu. Dace da dawowa zuwa irin wannan ƙirar raguwar exponential.
5. Haɗin Tsari: Yi XRD akan yanayin da aka jika da haske (canja wurin samfurin da sauri) kuma sake yin bayan dawowa cikakke a cikin duhu don tabbatar da raguwar kololuwa mai juyawa.

6. Bincike Mai Zurfi & Ra'ayi na Kwararru

Babban Fahimta: Hoke et al. ba kawai sun sami sabon yanayin lalacewa ba; sun gano rashin kwanciyar hankali na aiki na asali wanda ke cikin perovskites na gaurayawan halide a ƙarƙashin son rai. Ƙarfin lantarki na tantanin ku ba a bayyana shi da fim ɗin da kuka ƙera ba, amma da fim ɗin da ya samo asali a ƙarƙashin haske. Wannan canji ne ga yadda ake fahimtar daidaitawar halide.

Kwararar Hankali: Hankali yana da kyau kuma yana da laifi. 1) Kwayoyin gaurayawan halide suna rashin aiki akan $V_{OC}$. 2) Hasken yana haifar da juyawa zuwa ja a cikin PL zuwa wani ƙayyadadden, ƙarancin makamashi. 3) Hasken kuma yana haifar da raguwar kololuwar XRD. 4) Ƙarshe: Hasken yana tafiyar da rabuwar lokaci mai juyawa zuwa I-mai wadata (ƙananan-$E_g$, haɗuwa mai yawa) da yankuna masu wadatar Br. $V_{OC}$ an ɗaure shi da tarkokin masu wadatar I. Bayani ne kai tsaye, na injiniya ga babban hanyar aiki.

Ƙarfi & Kurakurai: Ƙarfin takardar shine haɗin kai na fannoni daban-daban na bayanan gani da tsari don ba da shawarar ƙirar jiki mai jan hankali. Binciken juyawa yana da mahimmanci—ba lalacewa maras juyawa ba ne, amma ma'auni mai ƙarfi. Duk da haka, aikin 2015 shine rahoto na phenomenological. Yana hasashe akan ƙaura ion amma baya tabbatar da shi tare da dabarun kai tsaye kamar ¹²⁷I NMR ko in-situ TEM, kuma baya ƙirƙira ainihin ƙarfin tuƙi (misali, damuwa, samuwar polaron). Aikin gaba na Slotcavage, Snaith, da Stranks zai gina akan wannan, yana nuna cewa lamari ne na duniya a cikin tsarin gaurayawan halide da ma gaurayawan cation, wanda ya ƙara tsananta ta hanyar ƙarfin haske mafi girma da ƙananan yanayin zafi—wani batu mara hankali wannan takarda ta farko ta rasa.

Abubuwan Fahimta masu Aiki: Ga masu bincike da masu haɓaka kasuwanci, wannan takarda tana ƙara ƙarar gargadi: kawai daidaita halide don bandgap tarko ne (da ma'ana). Martanin al'umma, wanda ke bayyana a cikin wallafe-wallafen gaba, ya rabu: 1) Kauce wa matsalar: Mayar da hankali kan iodide mai tsabta (FAPbI₃) don manyan sel, ta amfani da injiniyan cation (misali, gaurayawan Cs, FA, MA) don kwanciyar hankali, ba gaurayawan halide don bandgap ba. 2) Rage matsalar: Bincika dabarun hana ƙaura ion ta hanyar ƙetare iyakar hatsi, injiniyan damuwa, ko amfani da manyan cations na wurin A waɗanda ba su da motsi. Don sel tandem waɗanda ke buƙatar babban bandgap (~1.8 eV) saman tantanin, binciken ya koma zuwa madadin ƙarancin bromide ko maras bromine (misali, gawa na tin-lead). Wannan takarda ta tilasta juyawa na dabarun a cikin falsafar ƙira na kayan aiki.

7. Aikace-aikace na Gaba & Hanyoyin Bincike

Yayin da ƙalubale ne ga photovoltaics, fahimta da sarrafa rabuwar lokaci da hoto ke haifarwa yana buɗe kofofi a wasu fagage:

• Photonics Mai Shirye-shirye: Canjin tsari mai juyawa, wanda aka rubuta da haske, ana iya amfani da shi don ƙwaƙwalwar gani ko abubuwan sauyawa inda takamaiman alamu na haske ke bayyana hanyoyin gudanarwa masu ƙarancin bandgap.
• Diodes Masu Fitowa da Hasken (LEDs): Ana iya amfani da rabuwa mai sarrafawa don ƙirƙirar cibiyoyin fitar da makamashi mai ƙarancin makamashi don fitar da bakan gaba ko farin haske daga kayan aiki ɗaya.
• Bincike na Asali: Tsarin yana aiki azaman abin koyi don nazarin jigilar ion da hoto ke haifarwa da sauye-sauyen lokaci a cikin semiconductors masu laushi, ionic.
• Hanyoyin Binciken PV na Gaba: Ƙoƙarin na yanzu suna mai da hankali kan:
  1. Haɓaka dabarun daidaitawar kinetic ta amfani da ligands na saman ko tsarin heterostructure 2D/3D don hana ƙaura ion a lokutan aiki.
  2. Bincika madadin perovskites masu faɗin bandgap tare da rage motsin halide, kamar waɗanda ke da gaurayawan cations (Cs/FA) ko perovskites masu girma kaɗan.
  3. Amfani da filaye na waje (lantarki, damuwa) don hana ƙarfin tuƙi na hoto don rabuwa.

8. Nassoshi

1. Hoke, E. T. et al. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chem. Sci. 6, 613–617 (2015). DOI: 10.1039/c4sc03141e
2. Slotcavage, D. J., Karunadasa, H. I. & McGehee, M. D. Light-Induced Phase Segregation in Halide-Perovskite Absorbers. ACS Energy Lett. 1, 1199–1205 (2016).
3. National Renewable Energy Laboratory (NREL). Best Research-Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html (An ziyarta akai-akai, yana nuna haɓakar inganci bayan 2015).
4. Stranks, S. D. & Snaith, H. J. Metal-halide perovskites for photovoltaic and light-emitting devices. Nat. Nanotechnol. 10, 391–402 (2015).
5. Bischak, C. G. et al. Origin of Reversible Photoinduced Phase Separation in Hybrid Perovskites. Nano Lett. 17, 1028–1033 (2017).